The President of the United States under Article 2, Section 3 of the Constitution ". . .may, on extraordinary occasions, convene both Houses, or either of them . . ." for extraordinary circumstances.
If the President decides to take action against ISIS and US military personnel are in harms' way, the United States Congress should not be in recess for any reason. The legislative branch enjoys far too much time away from their D.C. offices & should be forced to remain/return to Washington D.C. by the President each time either house attempts to recess for as long as there is military action against or associated with ISIS.
It's about time our elected government leaders are held accountable by constituents and are forced to focus on the nation's problems instead of their re-election goals.